linux-kernel - Re: [PATCH 02/20] ext4: prevent partial update of the extents path

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Message-ID: <20240724185358.jv7qehigpj7oelgd@quack3>
Date: Wed, 24 Jul 2024 20:53:58 +0200
From: Jan Kara <jack@...e.cz>
To: libaokun@...weicloud.com
Cc: linux-ext4@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca,
	jack@...e.cz, ritesh.list@...il.com, linux-kernel@...r.kernel.org,
	yi.zhang@...wei.com, yangerkun@...wei.com,
	Baokun Li <libaokun1@...wei.com>,
	zhanchengbin <zhanchengbin1@...wei.com>
Subject: Re: [PATCH 02/20] ext4: prevent partial update of the extents path

On Wed 10-07-24 12:06:36, libaokun@...weicloud.com wrote:
> From: Baokun Li <libaokun1@...wei.com>
> 
> In ext4_ext_rm_idx() and ext4_ext_correct_indexes(), there is no proper
> rollback of already executed updates when updating a level of the extents
> path fails, so we may get an inconsistent extents tree, which may trigger
> some bad things in errors=continue mode.
> 
> Hence clear the verified bit of modified extents buffers if the tree fails
> to be updated in ext4_ext_rm_idx() or ext4_ext_correct_indexes(), which
> forces the extents buffers to be checked in ext4_valid_extent_entries(),
> ensuring that the extents tree is consistent.
> 
> Signed-off-by: zhanchengbin <zhanchengbin1@...wei.com>
> Link: https://lore.kernel.org/r/20230213080514.535568-3-zhanchengbin1@huawei.com/
> Signed-off-by: Baokun Li <libaokun1@...wei.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext4/extents.c | 31 +++++++++++++++++++++++++++----
>  1 file changed, 27 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index bff3666c891a..4d589d34b30e 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -1749,12 +1749,23 @@ static int ext4_ext_correct_indexes(handle_t *handle, struct inode *inode,
>  			break;
>  		err = ext4_ext_get_access(handle, inode, path + k);
>  		if (err)
> -			break;
> +			goto clean;
>  		path[k].p_idx->ei_block = border;
>  		err = ext4_ext_dirty(handle, inode, path + k);
>  		if (err)
> -			break;
> +			goto clean;
>  	}
> +	return 0;
> +
> +clean:
> +	/*
> +	 * The path[k].p_bh is either unmodified or with no verified bit
> +	 * set (see ext4_ext_get_access()). So just clear the verified bit
> +	 * of the successfully modified extents buffers, which will force
> +	 * these extents to be checked to avoid using inconsistent data.
> +	 */
> +	while (++k < depth)
> +		clear_buffer_verified(path[k].p_bh);
>  
>  	return err;
>  }
> @@ -2312,12 +2323,24 @@ static int ext4_ext_rm_idx(handle_t *handle, struct inode *inode,
>  			break;
>  		err = ext4_ext_get_access(handle, inode, path + k);
>  		if (err)
> -			break;
> +			goto clean;
>  		path[k].p_idx->ei_block = path[k + 1].p_idx->ei_block;
>  		err = ext4_ext_dirty(handle, inode, path + k);
>  		if (err)
> -			break;
> +			goto clean;
>  	}
> +	return 0;
> +
> +clean:
> +	/*
> +	 * The path[k].p_bh is either unmodified or with no verified bit
> +	 * set (see ext4_ext_get_access()). So just clear the verified bit
> +	 * of the successfully modified extents buffers, which will force
> +	 * these extents to be checked to avoid using inconsistent data.
> +	 */
> +	while (++k < depth)
> +		clear_buffer_verified(path[k].p_bh);
> +
>  	return err;
>  }
>  
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR